Re: [patch] add module parameter to provide hardware-calibrated coordinate data for MicroTouch/3M touchscreens

[Vojtech Pavlik <vojtech@suse.cz>]

On Thu, Nov 13, 2008 at 03:22:52PM -0500, Dan Streetman wrote:

> Note that the Y axis is inverted as reported by the touchscreen, so
> this reverses the Y min and max (0xffff for the min, 0 for the max).
> This works fine on my system using the X evdev driver.

> +	// Default min/max xy are the raw values, override if using hw-calib
> +	if (hwcalib_xy) {
> +		input_set_abs_params(usbtouch->input, ABS_X, 0, 0xffff, 0, 0);
> +		input_set_abs_params(usbtouch->input, ABS_Y, 0xffff, 0, 0, 0);

While it does work with the X evdev, please don't do it, and instead do
the inversion before reporting ABS_Y. Linux input devices should follow
the (USB) HID specification of axis direction and stick to it. The
behaviour with reversed min/max is undefined.

-- 
Vojtech Pavlik
Director SuSE Labs